Blowing in a bottle: from youtube to sound file

Remember: in the Fall, I invited you to solve a science of sound problem. In Rico Loop's video, the aim is to find out how much he drinks in between the moments when he blows different pitches in the bottle.

A first step toward solving the problem consists in getting a sound file out of the youtube video ; then you will be ready to analyze the sound.

Of course, you can use any kind of "youtube to mp3" software, but I want to show you a more general approach: using audio routing software. Although it requires a little more effort, you will then be able to record any audio coming out of any piece of software in your computer into a sound file. Here is the idea:

Internal audio routing software

The two open source options most used by musicians are:

  • Jack, a flexible audio connection kit, available for Mac, Windows, Linux, and more operating systems!
  • Soundflower, only available for Mac.

There are plenty of resources online to learn how to use these tools, so I'm just going to show here a couple of screenshots with Soundflower settings to record a Mac's sound output.
First, using the Sound preferences, route the computer's default output to Soundflower 2ch - after completing this step, you do not hear the Mac's sound output, it is routed to Soundflower.

Next, if you want to hear the sound, route Soundflower 2ch to your default output - you need to use the Soundflower menu showing up when you launch the SoundflowerBed application:

Now, any default audio output goes to your speakers, but only after traveling on the "Soundflower 2ch" channel. Just record whatever passes on this channel with any audio recording software, for instance with Quicktime Player:

Hit record, launch the youtube video ; stop recording when the video is over, and voilà!

Next step in the quest: getting the frequencies from the sound file...


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